Celery Seeds: The Trick That Gets Them to Germinate

Celery seeds are notoriously difficult to germinate, and on my first attempt they failed miserably; not one sprouted celery seed could be seen. After tweaking my method for the following year’s attempt at germinating celery seeds I achieved an excellent germination rate and finally succeeded!

But the work doesn’t stop there; celery seedlings take time and care to become edible, delicious stalks that we all appreciate. In this article, I’ll show you how you can give your celery crop an early headstart.

Celery seeds require three things in order to germinate: temperature of 70degF, constant moisture and direct light.

 To ensure constant humidity use plastic wrap or a dome. Sprinkle the seeds on top of a soil mix like coco coir and leave them exposed or cover with perlite. Place under lights or a windowsill.

That’s all there is to sprouting celery seeds in a nutshell – and it works just as well for celeriac. Now let’s take a closer look to make sure you get all the steps right:

Celery seed germination conditions

Ideal temperature

As I mentioned, celery seeds, like most vegetable seeds, love a good mellow room temperature of about 70°F (21°C) to germinate.

Celery can be grown both as a spring crop and a fall crop. It needs about 3 to 4 months to reach maturity and plenty of cool weather. For this reason, the only way to grow celery as an early crop is to start the seeds well before the last frost: 10 to 12 weeks before, to be exact.

That’s right, you should start your celery seeds at around the same time as your peppers and eggplants if you want an early crop because celery grows VERY slowly – it’s a 4-month project from germination to harvest. And the only way to do that is to start them indoors, in a controlled environment.

Constant moisture

I don’t know about you, but I find that *constant* moisture is the hardest thing to achieve in gardening indoors, as opposed to raised beds. My containers and module trays either dry out or I overwater – it’s a neverending cycle.

The trick with ensuring constant humidity is to pre-moisten the soil mix, sow your seeds, spray with water and then cover the container with either plastic wrap, a transparent plastic lid or a humidity dome. Anything that traps the moisture in and is see-through does the job.

And then LEAVE IT ALONE. Check the seeds daily for signs of germination, but don’t water too often, unless the surface looks dry. Overwatering is just as bad for tiny seeds like celery.

Grow lights vs. Windowsill

Celery seeds need light to germinate. That’s the most important fact that new gardeners are often unaware of. Here’s what this means for your method of sowing. You could:

• Cover the seeds with a very thin layer of seed starting mix;
• Not cover the seeds at all (but you risk drying them out if you’re not careful);
• Cover with a layer of perlite or vermiculite that leaves the light through (this trick works well for germinating herbs like rosemary, basil, thyme, etc).

Now that you have your seeds semi-exposed, it’s time to place them under grow lights. Since I use my grow lights for other seedlings as well, I keep them on a 16hrs ON – 8hrs OFF schedule. These are strong lights and help me get sturdy celery seedlings.

Alternatively, you can place your containers on a windowsill, especially if it’s sunny all day long, but you risk getting leggier seedlings. Don’t worry, you can fix this at a later stage.

How long do celery seeds take to germinate?

Celery seeds take anywhere from 2 to 3 weeks to germinate, so BE PATIENT! You’ll see a few sprouts push up from underneath the plastic wrap because not all of them will germinate at the same time. Once half of them have sprouted, remove the wrap, lid or dome and keep misting the soil mix from above until all seeds have germinated.

Once you have tiny seedlings, start watering them from below – but be careful not to overwater. Here’s a useful resource on how to properly water young seedlings.

If your celery seeds take longer than 3 weeks to germinate, it’s either too cold, you’ve allowed the soil surface to dry out, they don’t have access to light, or you have old seeds. As for seed age, celery seedlings can last for up to 5 years, so check your seed pack for the expiration date.